1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to an ultra wide band (UWB) device and a detect-and-avoid (DAA) method thereof, and more particularly, to an UWB device and a DAA method thereof which guarantees communication quality by avoiding interference with another device when transmitting and receiving UWB radio signals.
2. Description of the Related Art
Ultra wide band (UWB) is a wireless communication technology used to transmit and receive data through wireless access to PC, peripherals and/or home appliances in a limited space such as an office or home. UWB-applicable devices include almost every electronic product commonly used, such as a portable storage device, a printer, a camera, a mobile terminal, a game console, a vehicle, a computer, a speaker, a video device, and television (TV).
According to its characteristic, the UWB communicates using short pulses and enables information delivery at a very high rate of hundreds of megabits per second (Mbps) over a short range, for example within 10 m, using a wide frequency band of 500 MHz or so.
The frequency band of the UWB is divided into a lower band of about 3 GHz˜about 5 GHz and an upper band of about 6 GHz˜about 10 GHz. Band between the lower band and the upper band is unoccupied to avoid interference with existing wireless LAN (IEEE 802.11a) communications.
The lower band faces an interference problem with existing wireless service frequencies, and such interference may cause performance degradation of the existing wireless services. To prevent this, it is mandatory in every country, except the U.S.A., to adopt a detect-and-avoid (DAA) method in the lower band of the UWB band to protect existing wireless services. Yet, the DAA introduction has used some (e.g., about 4.2 GHz˜about 4.8 GHz in South Korea) of the lower band for several years for the sake of development of the DAA technology.
UWB communication technology can be divided to multiband orthogonal frequency division multiplexing (MB-OFDM) and direct sequence code division multiple access (DS-CDMA). The MB-OFDM splits the lower band into a plurality of sub-channels of about 500 MHz bandwidth and communicates through the frequency hopping between the bands, whereas the DS-CDMA splits the UWB frequency band to two bands and substitutes a bit string of each band with a 24-bit codeword. The MB-OFDM divides the lower band to three channels by 528 MHz as shown in FIG. 1. The width of the channel may differ in different countries.
However, while transmitting and receiving radio signals by selecting a channel through frequency hopping, when radio signals are transmitted and received to and from another device in the same channel, a device communicating using MB-OFDM suffers signal interference with another device. To avoid this, it is required to lower the transmit (Tx) output below −70 dBm/MHz which is the minimum output of the UWB band. However, with this low output, it is hard to accomplish high speed communication which is a goal of UWB communication. Hence, related art UWB communications employing the DAA method do not permit the frequency hopping which is used practically in MB-OFDM.